Effect of Binders on the Dissolution Rate and Dissolution Efficiency of Ritonavir Tablets

Ritonavir, a widely prescribed anti-retroviral drug, belongs to Class II under 'BCS' and exhibit low and variable oral bioavailability due to its poor aqueous solubility. Ritonavir is practically insoluble in water and aqueous fluids. Its aqueous solubility was reported to be 2.56 mg/100 ml. As such oral absorption of ritonavir is dissolution rate limited and it requires enhancement in solubility and dissolution rate for increasing its oral bioavailability. In the case of poorly soluble drugs formulation variables greatly influence their dissolution rate and bioavailability from solid dosage forms. The objective of the present work is to study the effect of seven binding agents on the tablet qualities and dissolution rate of ritonavir tablets to optimize the formulation of ritonavir tablets. Compressed tablets each containing 100 mg of ritonavir were prepared by conventional wet granulation method using seven binders namely acacia, sucrose, PVP, methyl cellulose, HPMC, starch paste and gelatin and the tablets were evaluated for content of active ingredient, hardness, friability, disintegration time, dissolution rate and dissolution efficiency. The binder used has significant influence on the tablet qualities and dissolution rate of ritonavir from the tablets. The order of performance of binders based on increasing dissolution rate and dissolution efficiency was acacia > starch paste > sucrose > PVP >gelatin > HPMC > MC. Tablets formulated with acacia, starch paste, and sucrose exhibited higher dissolution rates and dissolution efficiency values fulfilling all other official (IP) and GMP requirements of compressed tablets. Overall acacia, starch paste, sucrose and PVP were found to be suitable binders for ritonavir tablets.